Absorption of a femtosecond laser pulse by metals and the possibility of determining effective electron—electron collision frequencies

Thermal emission of electrons under irradiation of a gold target by a femtosecond laser pulse

“…The parameters a and b, known with a low degree of accuracy, are taken equal to 1 and 2, respectively (cf. the data of [15]). Finally, in accordance with the experimental data [13], the quantities e 0 ' (w) and e 0 "(w) corresponding to the frequency w -1.5 ´ 10 15 s -1 are equal to 11 and 1.2.…”

“…To this end, we consider the numerical solution to equations (15), (20) when a femtosecond pulse of a Cr : forsterite laser with a carrier frequency w -1.5 ´ 10 15 s -1 irradiates a target made of gold. We assume that the flux density varies according to the law ( )…”

Generation of nonlinear currents and low-frequency radiation upon interaction of a laser pulse with a metal

“…This approach is certainly justified if the characteristic velocity of the electrons in the high-frequency field is less than their thermal velocity, which leads to limitation of I L . In particular, under conditions of a high-frequency skin effect, for which we present the estimates, the energy flux density limitation has the form I L < 0.125cnk B T, where k B is the Boltzmann constant [12]. For the gold target, when n -6 ´ 10 22 cm -3 and the electron temperature typical for the fluxes under consideration is T > 1000 K, we obtain I L < 3 ´ 10 12 W cm -2 .…”

Reflection of a probe pulse and thermal emission of electrons produced by an aluminum film heated by a femtosecond laser pulse

“…We will find the reflection coeffi cient in (27) at moment t in the case of a weakly heated film from the relation (28) where the absorption coefficient (29) and the transmission coefficient |T(ω)| 2 (10) corre spond to angle of incidence θ = 0. According to expressions (10) and (27)- (29), only the contribution to |R(ω, Δt)| 2 proportional to the electron collision rate ν(z, t) depends on Δt. The electron collision rate changes during heating of electrons and the lattice caused by the pump pulse absorption.…”

“…These experiments were usually performed by the pump-probe pulse method by vary ing the probe pulse delay [6][7][8][9]. The absorption fea tures of femtosecond pulses observed in many experi ments were explained in the model taking into account the fast heating of electrons in the skin layer followed by their cooling due to heat removal from the skin layer and by energy transfer to the lattice [10][11][12]. The detailed description of the electron temperature evo lution was used to interpret the thermal emission of electrons from bulk metal samples heated by femto second pulses [13,14].…”